This invention relates to brake systems for heavy vehicles, such as trucks, road tractors, trailers, and the like, and it has particular reference to a semi-automatic mechanism by which the brakes on a standing vehicle can be positively set and locked, and maintained locked independently of the air or hydraulic system for normal vehicle braking. The invention is related to that disclosed in U.S. Pat. No. 3,482,666, to Walter Case and William Frank Benefield, dated Dec. 9, 1969.
An object of the invention is to provide a safe and dependable mechanism by which the brakes of a heavy vehicle, when set by air or hydraulic pressure, can be readily and easily locked and maintained against involuntary release to prevent accidental movement of the vehicle while parked or standing.
Another object of the invention is to provide a simple, rugged, and economical device which can be readily installed on existing equipment by a mechanic of ordinary skill.
Yet another object of the invention is to provide a mechanism which is self-adjusting and capable of maintaining maximum efficiency of the brakes at all times, by compensating for brake band wear and loss of actuating fluids.
A further object of the invention is to provide a brake locking mechanism having manual means for disengaging the mechanism in the event of failure of the fluid system.
These objects are accomplished in a brake locking mechanism for use with a fluid operated brake system which includes, for each wheel unit, a brake, actuator chamber and a brake actuator rod operatively connected to the wheel unit brake and which is reciprocated by said brake actuator chamber. The locking mechanism includes a casing adapted to be mounted in association with the actuator chamber, and having a first passage therethrough for accommodating the brake actuator rod for reciprocating movement, and a second passage transverse to and communicating with the first passage. The brake actuator rod is provided with longitudinally spaced transverse teeth; and a pawl rod is supported and guided for reciprocating movement in the second passage, the pawl rod having pawl means at one end for engagement with the rack teeth. The casing includes a cylinder chamber, with a piston being disposed in the chamber for reciprocating movement. Means is provided for coupling the piston means to the pawl rod. A spring is coupled to the pawl rod for urging the pawl rod in a first direction relative to the first passage, to engage the pawl means with the rack teeth; and conduit means is provided for introducing pressurized fluid into the cylinder to act on the piston for urging the pawl rod in a second direction relative to the first passage, to disengage the pawl means from the rod teeth.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.